1. Field of the Invention
The present invention relates to a fuel supply device of an engine.
2. Description of the Related Art
In a known "air blast" valve, the opening and closing operation of a nozzle opening is electromagnetically controlled by a needle to inject fuel by pressurized air. The nozzle opening is formed on one end of an injection chamber, a pressurized air passage is connected to the other end of the injection chamber, and a fuel supply port is formed in the injection chamber between both ends thereof. After fuel is injected from the fuel supply port, the needle opens the nozzle opening, whereby the fuel thus injected is injected from the nozzle opening of the air blast valve together with pressurized air (see International Publication No. WO85/00854).
When an air compressor is used for supplying pressurized air to the air blast valve, the air compressor must be lubricated to prevent overheating and subsequent damage to the compressor. When, however, the air compressor is lubricated, the lubrication oil is contained in pressurized air discharged from the air compressor. Accordingly, a problem arises in that this ubrication oil flows into a combustion chamber from the air blast valve. Also, if the lubrication oil flows into the air blast valve, the lubrication oil forms a hardened layer in the valve. Furthermore, when the air compressor is lubricated with engine oil from the crankcase of an engine, a problem arises in that the consumption of engine oil is increased.